1. Field of the Invention (Technical Field)
The invention relates to manufacturing three dimensional objects, and more particularly to an apparatus and method of forming three dimensional objects from a fluid medium using a high speed electron beam to harden the fluid medium in a predetermined pattern.
2. Background Art
Rapid prototyping is the technology of creating arbitrarily shaped parts. In general, this technology has the ability to produce enclosed volumes (like a can) in contrast to such processes as multi-axis milling which can only produce simply connected volumes (like a cup instead of a can, which is simply connected to the outside of the cup). If this technology is fast and accurate enough it can replace a variety of other techniques such as molding, and in many cases eliminate bonding of multiple pieces of material.
Present rapid prototyping technologies, as disclosed in U.S. Pat. No. 4,575,330 to Hull and U.S. Pat. No. 4,929,402 to Hull, use lasers or powder streams at high cost, and with slow processing rates. The processing rate of the most commonly used machines produces a xc2xc scale cylinder head of size of order  less than 1000 cubic cm in 4.5 hours. Such a part will cost in excess of $1000. By using the present invention, the cost level is comparable to other types of machining.
Laser-based rapid prototyping works by using a laser to cure a liquid. The laser""s position on the liquid is moved by mirrors, and limited by a fundamentally low cure rate, and by the rate at which the laser mirrors can be moved. The reasons for the low cure rate are low laser power (a typical existing machine has 1 W of laser power) and the relatively low rates of conversion of laser photons to curing power. Other variants use technology analogous to ink jet printing yielding parts which are produced somewhat faster, but with inferior mechanical properties. All existing techniques are limited in their speed to speeds too low for parts"" production.
In accordance with the present invention, there is provided an apparatus and method for creating an arbitrarily shaped part. The preferred apparatus of the invention is a rapid prototyping/manufacturing apparatus comprising at least one electron beam, a means to focus said at least one electron beam, a means to electromagnetically steer said focused at least one electron beam onto a substance to be solidified and a control means to control said at least one electron beam and said means to electromagnetically steer said focused at least one electron beam.
The preferred method for creating an arbitrarily shaped part comprises the steps of providing at least one electron beam, focusing the at least one electron beam onto the substance to be solidified, steering the at least one electron beam electromagnetically and controlling the at least one electron beam and the electromagnetic steering apparatus.
The primary object of the present invention is to create arbitrarily shaped plastic parts rapidly directly from a computer generated image.
Another object of the present invention is to process parts without the use of heat which distorts shapes as in molten plastic systems.
Yet another object of the invention is to create parts with such great rapidity that it can be used economically for production runs of parts.
The primary advantage of the present invention is it""s potential for high speed resulting from the intrinsic properties of electron beams. This reduces cost and makes possible the creation of production runs of complex parts.
Another advantage of the present invention is to overcome inertial effects in the control system which are associated with competing systems which rely on physical motion such as moving table systems, and moving mirror systems.
Yet another advantage of the invention is that it has the unique ability to vary the depth of plastic solidification unlike other methods of rapid prototyping.
Other objects, advantages and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.